Techniques for promoting plant growth enable early harvest of products and increase in plant biomass in a short period of time, and thus such techniques are very important for agriculture and forestry. Therefore, various attempts have been made to achieve the object, for example, by producing transgenic plants and knockout plants through optimization of cultivation conditions, treatment with plant hormones, modification of endogenous gene, and/or introduction of exogenous gene.
There have been inventions relating to enlargement of transgenic plant through introduction of exogenous gene. In most cases, the foreign genes conventionally introduced in techniques for enlarging plant were mainly genes encoding proteins involved in the photosynthesis pathway, for example, as described in Miyagawa et al., 2001, Nature Biotechnol, 19(10):965-969 and Chida et al., 2007, Plant Cell Physiol, 48(7): 948-957. Such method for enlarging plant through enhancement of the photosynthesis pathway is problematic. This is because even if the leaf photosynthetic capacity can be enhanced, only limited effects are exhibited in the whole plant. In addition, as a result of accumulation of photosynthetic products in leaves, the enhanced photosynthetic capacity becomes attenuated over time due to feedback effects.